Method of pre-forming and attaching metal pull tab metal can end rivet formation



Dec. 1, 1970 J. HENCHERT 3,543,391

METHOD OF DRE-FORMING AND ATTACHING MET-AL PULL TAB METAL CAN END RIVETFORMATION Original Filed Nov. 1, 1963 INVENTOR Jouu HENCHERT ATTORNEYS3,543,391 METHOD OF PRE-FORMING AND ATTACHING METAL PULL TAB METAL CANEND RIVET FORMATION John Henchert, Oak Park, Ill., assignor toContinental Can Company, Inc., New York, N.Y., a corporation of New YorkOriginal application Nov. 1, 1963, Ser. No. 320,763, now Patent No.3,416,221, dated Dec. 17, 1968. Divided and this application Aug. 21,1968, Ser. No. 754,215

Int. Cl. B21d 39/00 US. Cl. 29-509 3 Claims ABSTRACT OF THE DISCLOSUREThis disclosure relates to a method of securing a pull tab to aremovable panel portion of a container wherein the removable panelportion is provided with the integral rivet. The pull tab is providedwith an aperture therein of a diameter less than the diameter of thebase of the rivet, after which the pull tab is flared about the openingtherein so that the metal is stressed and the opening is increased to adiameter to receive the rivet. The pull tab is then seated down on thecontainer panel and the flared portion thereof is flattened with theopening therein again reducing in diameter and the pull tab tightlysqueezing the base of the rivet so as to inwardly stake the rivet, thusfacilitating the final staking or crimping of the rivet to secure thepull tab in place.

This application is a division of my application Ser. No. 320,763, filedNov. 1, 1963, now Pat. No. 3,416,221.

This invention relates in general to new and useful improvements inmethods of making easy opening containers, and more particularly relatesto a novel method of making a connection between a metal pull tab and atear strip portion of a can end.

At the present time containers are being provided with easy opening endswhich have portions thereof defined by tear strips which are removable.In order to facilitate the attachment of pull tabs to the tear stripswithout perforating the can ends, the tear strips are provided withintegral rivets which are utilized to secure the pull tabs to the tearstrips. However, difficulties have been encountered in the utilizationof such rivets in that there is not available suflicient metal for therivets to sutficiently hold the pull tabs against any accidental removalfrom the tear strips during the opening of the cans. This inventionrelates to a novel manner of securing a pull tab to a tear striputilizing an integral rivet wherein the pull tab is securely attached tothe tear strip by means of the rivet.

At the present time a tubular rivet is formed and the pull tab isprovided with a sufiiciently large opening to be easily positioned overthe rivet, after which the rivet is upset or deformed so as to flowoutwardly over the pull tab around the opening therein. There is nogripping action of the pull tab on the rivet and the rivet functionssolely to clamp the pull tab in place.

In accordance with this invention, it is proposed to provide a novelmethod of attaching a pull tab to a tear strip utilizing an integralrivet on the tear strip wherein prior to the crimping of the tubularrivet over the pull tab, the pull tab is caused to tightly grip the baseof the rivet, thereby greatly enhancing the connection between the pulltab and the tear strip.

Another object of this invention is to provide a novel connectionbetween a pull tab and a tear strip wherein the rivet receiving openingin the pull tab is temporarily enlarged by means of a flangingoperation, after which States Patent:

the pull tab is telescoped over the rivet and then is reformed to itsflat state so as to reduce the size of the opening therein with theresult that the metal of the pull tab defining the opening therein willclose around the rivet and effect a tight gripping thereof.

Another object of this invention is to provide a novel method ofassembling a pull tab on a can end wherein an integral rivet is utilizedto secure the pull tab in place, the method including the initialforming of the pull tab with an opening of a size too small to receivethe rivet, and wherein in subsequent operations, the opening istemporarily enlarged to receive the rivet and is later reduced so thatthe pull tab firmly grips the rivet at the base thereof and effects aprestaking operation on the rivet whereby a final staking of the rivetis facilitated and the pull tab is secured to the can end both by theclamping action of the rivet and by the gripping of the rivet by thepull tab.

A still further object of this invention is to provide a novel method ofsecurely achoring a pull tab on a can end by means of an integral rivet,the method including the forming of a pull tab having an opening thereinof a size insufficient to receive the rivet, flanging the pull tabaround the opening to temporarily increase the diameter of the openingin the pull tab to a dimension wherein the rivet is receivabletherethrough and after the pull ta'b has been positioned on the rivet,flattening out the flange on the pull tab wherein the diameter of theopening in the pull tab is reduced back to its previous size and themetal of the pull tab surrounding the opening firmly grips the base ofthe rivet and effects a necking down thereof wherein the rivet assumesan upwardly flared cross section which facilitates the final staking ofthe rivet over the pull tab.

With the above and other objects in view that will hereinafter appear,the nature of the invention will be more clearly understood by referenceto the following detailed description, the appended claims and theseveral views illustrated in the accompanying drawings:

In the drawings:

FIG. 1 is a top perspective view of a can end formed in accordance withthis invention.

FIG. 2 is a vertical sectional view on a large scale through the can endof FIG. 1 prior to the attachment of the pull tab thereto.

FIG. 3 is an enlarged fragmentary sectional view showing the relativesizes of the rivet and the opening in the pull tab.

FIG. 4 is an enlarged fragmentary plan View wherein the relativedimensions of the opening and the rivet are clearly shown.

FIG. 5 is an enlarged fragmentary sectional view similar to FIG. 3 andshows the pull tab after the flanging thereof surrounding the opening toeffect an increase in diameter in the opening.

FIG. 6 is a plan view of the pull tab and rivet arrangement of FIG. 5and shows the relative dimensions of the opening and the rivet.

FIG. 7 is a schematic view with parts in section of an apparatus whichfirst re-forms the pull tab and then stakes the rivet.

FIG. 8 is a vertical sectional view similar to FIG. 2 and shows theassembled pull tab and can end.

FIG. 9 is an enlarged fragmentary plan view with parts broken away andshown in section of the assembled can end and pull tab.

Referring now to the drawing in detail, it will be seen that there isillustrated in FIGS. 1 and 2 a can end which, with the exception ofbeing particularly formed to be of the easy opening type, is aconventional type of can end. This can end is generally referred to bythe numeral and as far as this invention is concerned, the can end 10includes an end panel 11 which has been formed with a score line 12defining a tear strip 13 which is particularly shaped for the dispensingof liquids therefrom. The tear strip 13 is provided adjacent one endthereof, the starting end of the tear strip, with a tubular rivet 14, asis best shown in FIG. 2. The tubular rivet 14 includes an upstandingcylindrical wall 15 and an end wall 16.

In accordance with this invention, it is proposed to utilize the tubularrivet 14 in the securement of a pull tab, generally referred to by thenumeral 17, to the tear strip 13 to facilitate the removal of the tearstrip 13. The pull tab 17 is illustrated as including a flat bodyportion 18 having a rivet receiving opening 19 therethrough adjacent oneend thereof, and the opposite end of the body 18 terminates in anupstanding flange 20 which defines a grip element to facilitate thelifting of the pull tab. It is to be understood that in accordance withthis invention, the structural details of the pull tab 17 may be varied.

It will be apparent from FIGS. 3 and 4 that the diameter of the rivetreceiving opening 19 is such that when the pull tab 17 is initiallyformed, it is not receivable over the rivet 14. It has been found thatwhen the rivet receiving opening of a pull tab is formed of sufficientsize to readily receive a rivet, a relatively loose fit results betweenthe rivet and the pull tab. After the rivet is crimped or headed tosecure the pull tab to the tear strip, the pull tab is secured in placesolely by the head of the rivet. A relatively large force is required toinitiate tearing the tear strip 13 from the end panel 11 and when thisforce is applied by lifting the free end of the pull tab, considerablepressure is concentrated against the head of the rivet. Should the headon the rivet be improperly formed or weakened during formation, the pulltab may be torn from the rivet prior to the actual opening of the can ofwhich the can end 10 is a part, thereby defeating its purpose.

In accordance with this invention it is proposed to obtain a mechanicalinterlock between the pull tab 17 and the rivet 14 independent of and inaddition to the crimping or heading of the rivet 14. In order toaccomplish this, the rivet receiving opening, as mentioned above, isinitially sized so that it will not receive the rivet 14. In order toassemble the pull tab 17 on the rivet 14, the portion of the pull tab 17surrounding the opening 19 is flared downwardly in the manner shown inFIG. 5. This downward flaring of the pull tab 17 results in theformation of a downwardly flaring flange 21 and an increase in thediameter of the rivet receiving opening 19. It will be apparent fromFIGS. 5 and 6 that the diameter of the rivet receiving opening 19 isthus increased in size to readily receive the rivet 14.

The pull tab 17, being temporarily deformed in the manner shown in FIGS.5 and 6, then may be loosely assembled over the rivet 14. Reforming orflattening the pull tab 17 back to its original shape shown in FIGS. 2and 3 results in straightening or removing the flange 20 and decreasingthe diameter of or resizing the opening 19 to approximately that shownin FIG. 3. Since the diameter of the opening 19 is less than that of therivet 14, it will be readily apparent that flattening the pull tab 17will compress and construct or neck in the cylindrical wall 15 of therivet formation at the base thereof in the manner clearly shown in FIG.7. This necking in or reforming of the rivet 14 at the base thereof bythe reformation of the pull tab causes the previous cylindrical wall 15to have an upwardly flared configuration, such as would result from aprestaking operation on the rivet. The rivet 14 is then finally crimpedover or headed to firmly clamp the pull tab 17 against the end panel 11,as is clearly shown in FIGS. 8 and 9.

It will be readily apparent from the foregoing description thatflattening or reforming the pull tab 17 to the position shown in FIG. 7,forms a strong positive mechanical connection between the pull tab andthe side wall of the rivet 14. In certain instances this connection maybe sufficient for removing the tear strip 13 by the pull tab 17 withoutany further deforming operation on the rivet 14 to provide it with ahead. However, the primary purpose of this invention is to provide adual connection for attaching the pull tab to the rivet. It will beapparent that by providing a mechanical connection between the pull taband the rivet independent of and supplemental to the clamping action ofthe rivet on the pull tab, the possibility of pulling the pull tab oflthe rivet during the opening operation on the can end will be greatlydecreased or eliminated.

Reference is once again made to FIG. 7 wherein there is shown apparatusfor effecting both the re-forming of the pull tab and the crimping orheading of the rivet. This apparatus, which is generally referred to bythe numeral 22, includes a back-up member 23 on which the end panel 11is seated with the rivet 14 overlying the backup member 23. It isunnecessary for the back-up member 23 to have a portion projecting intothe rivet 14 because when the pull tab 17 is re-formed, it will firmlygrip the base end of the rivet 14 and serve to support the rivet duringthe crimping or final staking of the rivet. However, if desired, theback-up member 23 could be provided with a short projection which wouldbe received within the rivet 14.

The apparatus 22 includes a punch unit which is generally referred to bythe numeral 24. The punch unit 24 includes a reciprocating head 25 whichmay be a part of a conventional punch press. The head 25 carries aninner punch member 26 on which there is mounted for relative slidingmovement an outer punch member 27. The outer punch member 27 is tubularand is of a diameter to clear the rivet 14 when it is in its finallycrimped or staked position of FIG. 8. The outer punch member 27 issecured on the inner punch member 26 for limited travel in aconventional manner not shown. The outer punch member 27 is resilientlyretained in an outer position with respect to the inner punch member 26by means of a coil spring 28 which encircles the inner punch member 26and bears against the head 25 and the outer punch member 27.

In the operation of the punch unit 24, the head 25 is brought down in anormal punching movement with the outer punch member 27 engaging thepull tab 17 around the rivet 14. The pressure exerted by the outer punchmember on the pull tab 17 is suflicient to re-form the pull tab 17 bythe flattening of the flange 21. As has been stated above, theflattening of the flange 21 results in the reduction of the diameter ofthe rivet receiving opening 19 so that the metal of the pull tab 17surrounding the opening 19 will tightly grip the rivet 14 at the basethereof and form a mechanical connection therewith. It will be readilyapparent that the relative diameters of the rivet 14 and the rivetreceiving opening 19 is such that a definite constriction of the rivet14 at the base thereof results and the rivet assumes a prestakedconfiguration. Further downward movement of the head 25 results in thecompressing of the spring 28 while the punch member 26 continues to movedownwardly. Since the rivet 14 is already initially staked by thenecking in operation, and the body 15 of the rivet is upwardly andoutwardly flared, a downward force on the end wall 16 of the rivet bythe inner punch member 26 results in the crimping or staking of therivet 14 in the manner clearly shown in FIG. 8. The mechanical interlockbetween the rivet 14 and the pull tab 17 is now complete.

From the foregoing description it will be evident that the inventionprovides for a better distribution of the force applied to the rivetformation by the pull tab when lifted so that the entire force is notconcentrated on the head of the rivet.

Dividing the force between the constriction and head formations of therivet provides a dual connection that reduces the force applied to thehead portion of the rivet. This contributes to avoiding separation ofthe pull tab from the rivet during the lifting operation that mightotherwise occur.

It is to be understood that the relative proportions of the can end, therivet and the pull tab have been exaggerated so as to clearly illustratethe invention and the manner in which the pull tab and rivet aredeformed.

Although only a preferred embodiment of the invention has beenspecifically illustrated and described here in, it is to be understoodthat minor variations may be made in the method of this inventionWithout departing from the spirit and scope thereof.

I claim:

1. A method of securing a pull tab to a tear strip of a containermember, said method comprising the steps of shaping the container memberto have an integral tubular rivet having a free end and a base endconnected to the container member, forming an opening in the pull tab ofa diameter less than the diameter of the rivet base end, deforming thepull tab around the opening therein to define a flared flangesurrounding the opening with the opening being offset from the originalposition thereof and the diameter of the opening increased to receivethe rivet free end, positioning the pull tab on the rivet, flatteningthe flange of the pull tab to reduce the diameter of the pull tabopening with the pull tab gripping the rivet base end and effecting anecking in of the rivet at the base end thereof, and then crimping therivet free end over the pull tab around the pull tab opening to furtherand securely attach the pull tab to the container member.

2. The method of claim 1 wherein said tubular rivet is cylindrical andthe diameter of the increased opening is sufficient to permit thecomplete passage of the rivet through the enlarged opening in the pulltab.

3. The method of claim 1 wherein the necking of the rivet at the basethereof is such whereby the rivet assumes a partially stakedconfiguration prior to the crimping of the rivet free end of the pulltab.

References Cited UNITED STATES PATENTS 1,675,328 7/1928 Borland.1,972,897 2/1931 De Lacy. 2,029,329 2/ 1936 Ljungstrom et al. 3,191,564-6/1965 Fraze 29509 XR CHARLIE T. MOON, Primary Examiner US. Cl. X.R.

